The invention relates to a boiler having a fire chamber which is cooled by water, a door which is likewise cooled by water and in which an opening for an oil or gas burner is located, and a water-cooled insert.
A boiler possessing these features is described in DE 40 16 880 A1. Here the entire fire chamber is cooled, namely the annular wall that surrounds the fire chamber in cylindrical fashion as well as the front door and rear face wall.
A warm-water boiler that has a fire chamber rinsed by water is described in DE-AS 1 579 940. This boiler, a hollow rotating body whose diameter increases toward the fire chamber door at the end of the fire chamber at which the door is located. A diffuser-type configuration of the cooling device is intended to be achieved through this measure, with the advantage of attaining a laminar flow of the heating gases, which is intended to reduce the development of noise. The heating surfaces of the boiler are also intended to be acted upon uniformly by the fuel gases, which should increase the efficiency of the boiler.
A steam boiler whose one face wall has a double-cone-shaped insert, and whose double wall has boiler water flowing therethrough, is described in DE-U-1 911 608. The cross-section of the insert tapers toward the interior of the boiler. With this cross-sectional shape, however, no flame can be generated with oil or gas burners. This construction is therefore not used in oil- or gas-fired boilers.